Method of constructing finned heat exchangers from bonded metal sheets



June 9, 1964 R. L. SOLNICK ETAL 3,135,037 METHOD OF CONSTRUCTING F INNED HEAT EXCHANGERS FROM BONDED METAL SHEETS Filed Oct. 31, 1955 2 Sheets-Sheet 1 Jllne 1964 R. L. SOLNICK ETAL 3,136,037

METHOD OF CONSTR UCTING FINNED HEA XCHANGERS FROM BONDED METAL SHEE Filed Oct. 31, 1955 2 Sheets-Sheet 2 Fig.7.

ROBERT L. LSOLN/CK /9 GORDON SM/TH (/20 INVENTOR.

United States Patent 3,136,037 METHGE) F CGNSTRUCTING FINNED HEAT EXCHANGERS FRGM BONDED METAL SHEETS Robert L. Solnici; and Gordon N. Smith, Whittier, Califi,

assignors, by direct and mesne assignments, to Olin Mathieson Qhernical Corporation, a corporation of Virginia Filed Oct. 31, 1955, Ser. No. 543,904 3 laims. (Cl. 29-1573) This invention relates generally to novel methods for constructing externally finned heat exchangers containing passages for conducting fiuid in heat exchange relation with the fins, and more particularly has to do with methods for extruding exterior fins of various types on metal sheets simultaneously with or subsequent to roll bonding of the sheets, or upon one or more softer sheets of metal cladding the outer surfaces of the roll bonded base sheets, either simultaneously with or subsequent to the cladding step.-

It is a major object of the invention to simplify the fabrication of finned heat exchangers of the type containing one or more passages for conducting fluid in heat exchange relation with the fins, the invention being directed to methods for extruding fins upon the surfaces of roll bonded sheets of metal prior to the expansion of the sheets to form the passages therein. The invention contemplates progressive extrusion of the fins as by rolling application of a die forceably against the exterior surface of a metal sheet, the sheet comprising either one of the roll bonded sheets, or against a softer layer of metal cladding a roll bonded sheet. Also, the scope of the invention includes performing the extruding step either coincidentally with or subsequently to roll bonding of the base sheets, or coincidentally with or subsequently to cladding the base sheets, the fins being formed in various sizes and configurations, as for example individually projecting fins or laterally elongated fins extending at angles to the interior passages.

Completion of heat exchanger fabrication involves expanding the passages formed in between the roll bonded sheets, as described in U.S. Patent 2,690,002 to Grenell. As explained therein, prior to roll bonding of the sheets weld-preventing material is selectively applied to the surfaces thereof according to the desired passage configuration, so that when the sheets are superposed and progressively bonded together, flattened unbonded passages will be formed to extend within the sheet-like body.

Following extrusion of the fins on the roll bonded sheets or upon the softer metal cladding the latter, the internalpassages may be expanded as by introducing sufiicient fluid pressure therein to physically displace the metal on opposite sides of the passages, for passing fluid therethrough in heat exchange relation with the fins.

Other features and objects of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following detailed description of the drawings, in which:

FIG. 1 is a plan view of the roll bonded metal sheet;

FIG. 2 is a section taken on line 2-2 of FIG. 1 showing the cladding layer on the roll bonded sheet;

FIG. 8 is a perspective showing the finished base sheet having fins extruded on one face thereof;

FIG. 9 is an enlarged section illustrating the method of simultaneously applying a cladding layer onto the base sheet and extruding fins in the cladding layer by the use of a roller type die;

FIG. 10 is a perspective of a modified form of rollertype die;

FIG. 11 is a section taken through a base sheet showing modified fins formed on the cladding layer as by the die shown in FIG. 10; and

FIG. 12 is a section taken on line 1212 of FIG. 11.

Referring to FIGS. 1 and 2, two metallic sheets 10 and 11 are shown in superposed and interruptedly'bonded together condition indicated by the interface 12 shown in broken lines. Prior to the bonding step, thin, narrow coatings of weld-preventing material such as wax or a mixture of graphite in water glass are. applied to one or both sheet faces to be bonded together according to the configuration of the passages 13 to be formed therebetween. After the bonding process, the weld-preventing material assumes the configuration shown by the broken lines 13 in FIG. 1 and by the interrupted heavy lines 13 in the plane of interface 12, the bonding process having the effect of enlarging the lateral dimension of the weld-preventing material.

The two sheets 10 and 11, which may for example comprise a relatively high strength aluminum alloy, may be bonded together to form a single sheet-like body 14 by the hot rolling process described in US. Patent 2,690,002, or the cold rolling process described in US Patent 2,212,481, the two sheets 10 and 11 being joined or bondedacross interface areas 12 but not across an expanded passages 13 formed by the weld-preventing material.

Following the roll bonding step, a relatively thinner layer of cladding material 15 may be affixed to at least one surface 16 of the sheet 14, as by wellknown cladnesium and 0.25 percent chromium, 148 containing 4.4

, percent copper, 0.8 percent silicon, 0.8 percent manga- FIG. 3 is a perspective showing one form of roller type die for extruding fins;

FIG. 4' is an enlarged section illustrating the method of extruding fins on a pair of cladding layers by the use nese and 0.4 percent magnesium, 248 containing 4.5 percent copper, 0.6 percent manganese, and 1.5 percent magnesium, 758 containing 1.6 percent copper, 2.5 'percent magnesium, 5.6 percent zinc and 0.3- percent chromium. As an alternative to cladding the roll bonded cladding layer 15 is illustrated in '4,'wherein a base roll bonded sheet 14 having a pair of cladding layers or laminations 15 adhering respectively to opposite faces thereof is passed between a pair of roller type dies 17.

Each of the latter has a continuous series of laterally elongated, circumferentially spaced ribs 18 formed around its circumference, the dies and ribs comprising a material substantially harder than the cladding metal so that as the dies are rotated the ribs will bite into the cladding layers effecting extrusion of the latter into the spaces between the ribs. As shown in FIG. 4 during extrusion by the die, the cladding layer is reduced in thickness at those portions thereof penetrated by the ribs 18, while intermediate portions of the cladding layer are extruded outwardly away from the base sheet 14 within the spaces between the ribs, thereby forming the laterally elongated and longitudinally spaced outwardly projecting fins 19. It is of course understood that any suitable lubricant may be introduced between the die and the cladding layer being fed thereto to facilitate cold flowing or extruding of the cladding metal.

A typical roller-type die having elongated triangularsection ribs spaced around its circumference is shown in FIG. 3. The die contains a large number of radial openings 119 communicating between the open interior of the die and the base portions between the ribs 18, the openings serving to pass air trapped between the ribs during extrusion of the fins.

After formation of the fins, the unexpanded passages 13 within sheet 14 are pressure expanded by introducing pressurized liquid or gas into the passages through either of the tubes 20 shown connected into the side of the base sheet 14 in FIG. 1, as discussed in US. Patent 2,690,002. The resulting form of the sheet and fins is shown in FIGS. 5 and 6, the former depicting a sheet having fins formed on one face thereof, while the latter showing fins on opposite sides, the fin portions on opposite sides of the expanded passageway 13 being outwardly arcuately displaced in conformance with expanded base sheet portions 21.

Referring to FIGS. 7 and 8, the same die 17 is shown in process of extruding laterally elongated and longitudinally spaced fins 19 on a face of the base sheet 14 itself, in the absence of any cladding layer thereon. The resultant base sheet in the form of a completed heat exchanger is shown in FIG. 8 after expansion of the passages 13, its appearance being much like that of the sheet shown in FIG. 5. Also illustrated in FIGS. 7 and 8 are a pair of thin layers 22 of material cladding respectively the inner faces 23 of base sheets it) and 11, the cladding layers being bonded across interface 24 shown by the broken line, as by the same roll bonding process discussed above. With weld-preventing material appropriately applied between the thin cladding layers 22 in desired passage configuration, the latter and sheets 10 and 11 may be expanded at the passages 13 which, as a result, will be bordered by the thin cladding layers. Use of a non-corrodable cladding material for this purpose permits use of the completed heat exchanger for passage of corrosive fluids through the expanded passages 13 formed therein.

In FIG. 9, the same roller-type die 17 is shown being used not only for extruding fins 19 on the cladding layer 15, but also as a pressure roller urging the cladding layer into holding engagement against the outer face 120 of the base sheet 14 to accomplish the actual cladding operation. For this purpose, both the base sheet and cladding layer may be advanced in one direction past the rotating die with suificient normal pressure being exerted by the roller against the cladding layer to accomplish both fin extrusion and cladding of the base sheet.

A modified roller-type die is shown in FIG. 10 to contain a large number of radially extending tapered openings 25 communicating between the outer periphery of the die and the smaller air outlet openings 119 communicating with the open interior of the die. Tapered openings 25 have their largest diameters at the die periphery and are arranged in laterally and longitudinally spaced relation, so that when the die is progressively rotated against the cladding layer on base sheet 14 the cladding layer will be reduced in thickness, the excess metal fiowing outwardly into the openings to result in the formation of laterally and longitudinally spaced fins 26 shown in FIGS. 11 and 12. Such fins are characterized as projecting away from the base sheet 14, and may be descriptively referred to as pin fins. Finally, the passages 13 may be expanded by sutiicient fluid pressure, enlarging and arcuately displacing the fins opposite the passages.

In use, an eficient heat exchange relation may be established between the extended surface fins formed on the heat exchanger and the passages 13 through which fluid is passed, the design of the exchanger being directed toward its use in flowing fluid through passages 13 for heat exchange with a gas passed externally over the fins.

We claim:

1. The method of forming an extended surface heat exchanger from a first metal sheet having unexpanded passages extending therein substantially parallel to the sheet plane and a second metal sheet, including simultaneously progressively joining said sheets in facing relation and extruding interrupted surface portions of said second sheet relatively away from said first sheet to form outwardly extending spaced projections by progressive application of pressure to the outer sides of intermediate surface portions of said second sheet urging it into holding engagement with said first sheet and expanding said second sheet by introducing pressurized fluid into said passages adapting them for passing fluid therethrough in heat exchange relation with said projections.

2. The method of forming an extended surface heat exchanger from a first metal sheet having unexpanded passages extending therein substantially parallel to the sheet plane and a second sheet formed of relatively softer metal, including simultaneously progressively cladding said second sheet on said first sheet and extruding longitudinally interrupted and laterally elongated surface portions of said second sheet relatively away from said first sheet to form outwardly projecting longitudinally spaced and laterally elongated fins by progressive application of pressure to the outer sides of intermediate surface portions of said second sheet urging it into holding engagement with said first sheet, and expanding said second sheet by introducing pressurized fluid into said passages adapting them for passing fiuid therethrough in heat exchange relation with said projections.

3. The method of forming an extended surface heat xchanger from a first metal sheet having unexpanded passages extending therein substantially parallel to the sheet plane and a second sheet formed of relatively softer metal, including simultaneously cladding said second sheet onto said first sheet and progressively extruding laterally and longitudinally spaced surface portions of said second sheet relatively away from said first sheet to form a plurality of outwardly projecting laterally and longitudinally spaced fins by progressive application of pressure to the outer sides of intermediate surface portions of said second sheet urging it into holding engagement with said first sheet, and expanding said first sheet by introducing pressurized fluid into said passages adapting them for passing fluid therethrough in heat exchange relation with said fins.

References Cited in the file of this patent UNITED STATES PATENTS 1,992,297 Dewald Feb. 26, 1935 2,463,997 Rodgers Mar. 8, 1949 2,646,259 Powell July 21, 1953 2,646,971 Raskin July 28, 1953 2,690,002 Grenell Sept. 23, 1954 2,728,136 Fromson Dec. 27, 1955 2,732,615 Sandberg Jan. 31, 1956 2,740,188 Simmons Apr. 3, 1956 2,765,526 Sparkes et al Oct. 9, 1956 2,779,223 Schuster Ian. 29, 1957 

1. THE METHOD OF FORMING AN EXTENDED SURFACE HEAT EXCHANGER FROM A FIRST METAL SHEET HAVING UNEXPANDED PASSAGES EXTENDING THEREIN SUBSTANTIALLY PARALLEL TO THE SHEET PLANE AND A SECOND METAL SHEET, INCLUDING SIMULTANEOUSLY PROGRESSIVELY JOINING SAID SHEETS IN FACING RELATION AND EXTRUDING INTERRUPTED SURFACE PORTIONS OF SAID SECOND SHEET RELATIVELY AWAY FROM SAID FIRST SHEET TO FORM OUTWARDLY EXTENDING SPACED PROJECTIONS BY PROGRESSIVE APPLICATION OF PRESSURE TO THE OUTER SIDES OF INTERMEDIATE SURFACE PORTIONS OF SAID SECOND SHEET URGING IT INTO HOLDING ENGAGEMENT WITH SAID FIRST SHEET AND EXPANDING SAID SECOND SHEET BY INTRODUCING PRESSURIZED FLUID INTO SAID PASSAGES ADAPTING THEM FOR PASSING FLUID THERETHROUGH IN HEAT EXCHANGE RELATION WITH SAID PROJECTIONS. 